State Route 170 (SR 170) is a north–south running state route located in Mahoning and Columbiana counties in northeast Ohio. It runs within a few miles of the Pennsylvania border for much of its route as it passes through the eastern parts of the two counties. The southern terminus is at an interchange with U.S. 30, State Route 7, and State Route 11 near Calcutta, and the northern at U.S. 62 in Youngstown. ODOT extended the northern terminus from the previous point of Interstate 680, changing signs on July 16 and 17, 2008.